HSC Survey Results

Scots Bay Survey # 5 Results from 01/07/2024

Survey Details

4 commercial purse seiners conducted this fishing survey on 01/07/2024 starting at 21:00:00, which was 0.38 hours after hide tide.

All vessels ran two transects each in the Main Survey Box, and the Canada 100 ran four lines in the Northern Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 7,252mt, and with turnover applied 3,123mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-07-01 20:38:34 2024-07-01 23:37:46 -65.233 45.073 -64.725 45.240 SB 44.10 7.97
BP T02 2024-07-02 00:01:27 2024-07-02 01:50:30 -64.793 45.286 -65.197 45.147 SB 35.38 10.51
C1 T01 2024-07-01 20:54:40 2024-07-01 22:07:23 -65.045 45.252 -64.835 45.318 SB 18.50 8.24
C1 T02 2024-07-01 22:12:42 2024-07-01 23:22:17 -64.850 45.324 -65.052 45.263 SB 17.73 8.25
C1 T03 2024-07-01 23:29:01 2024-07-02 00:32:20 -65.051 45.276 -64.866 45.333 SB 16.19 8.28
C1 T04 2024-07-02 00:38:20 2024-07-02 01:34:55 -64.884 45.340 -65.049 45.289 SB 14.53 8.32
LB T01 2024-07-01 20:37:37 2024-07-01 23:59:21 -65.232 45.099 -64.753 45.262 SB 42.50 6.82
LB T02 2024-07-02 00:26:45 2024-07-02 02:33:11 -64.820 45.312 -65.234 45.167 SB 37.26 9.55
LM T01 2024-07-01 20:35:07 2024-07-01 23:39:41 -65.233 45.054 -64.711 45.227 SB 45.69 8.02
LM T02 2024-07-02 00:03:27 2024-07-02 02:31:40 -64.777 45.279 -65.232 45.123 SB 39.99 8.74

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LB T01 -35.5 -50.403 0.032
LM T01 -35.5 -54.370 0.013
LM T02 -35.5 -55.284 0.011
BP T02 -35.5 -56.953 0.007
C1 T03 -35.5 -57.123 0.007
BP T01 -35.5 -57.485 0.006
LB T02 -35.5 -57.845 0.006
C1 T02 -35.5 -58.203 0.005
C1 T04 -35.5 -61.065 0.003
C1 T01 -35.5 -61.078 0.003
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 538 -54.4256 0.0125 6,884.9664 86.8 94.9 2,213.76 32.15
Northern Box -35.5 82 -59.0138 0.0044 366.5553 13.2 5.1 83.62 22.81

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by LB, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by LB, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 78,662 2023-05-22 40,856.000 40,856 47,629 47,629
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767.329 108,783 98,582 92,772
Scots Bay 3 2024-06-02 93,804 89,523 2023-06-18 34,279.387 15,158 29,417 12,720
Scots Bay 4 2024-06-16 33,347 22,278 2023-07-02 11,744.776 5,113 9,330 3,622
Scots Bay 5 2024-07-01 7,252 3,123 2023-07-16 19,282.634 17,575 17,387 16,022
Scots Bay 6 NA NA NA 2023-07-30 4,549.933 1,904 3,474 1,093
Scots Bay 7 NA NA NA 2023-08-13 4,298.806 3,616 2,777 2,247
Scots Bay 9 NA NA NA 2023-09-10 3,053.669 2,916 3,219 0
Scots Bay 10 NA NA NA 2023-09-24 3,419.932 2,997 2,318 0
Scots Bay 8 NA NA NA 2023-08-27 2,896.659 2,300 1,612 1,224
Scots Bay 11 NA NA NA 2023-10-09 3,387.515 2,971 2,521 0
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,536.6 204,189 218,266 177,329
2024 Scots Bay 242,907.0 210,841 NA NA

Plankton, and CTD Data

Summary map

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number SB2024-09 SB2024-10
Ground SB SB
Date 01/07/2024 01/07/2024
Wind Direction (km/h) NE NE
Swell (m) 0 0
Air Temp (c) 21 21
Tow Details
Tow Start 19:07:00 19:26:00
Tow End 19:17:00 19:36:00
Start Lat 45.0545 45.0612
End Lat 45.06817 45.05250
Start Lon -65.24683 -65.21983
End Lon -65.22883 -65.20483
Avg Tow Depth (m) 8.916724 10.252992
Speed 6.5 5.4
Heading 97 129
Tide Direction with against
Other Data Collection
Flow Start 47495 98838
Flow End 98838 157450
No. Revolutions 51343 58612
Distance (m) 1379.74 1575.08
Volume 4334.455 4948.115
Secchi Disappear (m) 17 17
Secchi Reappear (m) 16 16

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2024-09, which was with the tide and had an average depth of 8.9167243m. The second tow is SB2024-10, which was against the tide and had an average depth of 10.2529915m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

Average vessel speed was 8.52. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

More than 2km of distance was cut from the planned lines; vessels are reminded to complete their assigned lines straight and without deviating or cutting corners short.